Team Scorpion is tasked with uncovering a mole inside the CIA whose judgment is clouded by matters of the heart and is being coerced into stealing deadly chemicals. Also, in preparation for the case, Paige gives Walter a flirting lesson.

Team Scorpion goes undercover on a cruise ship to locate and disable deadly stolen rockets. Meanwhile, as Valentine's Day approaches, Toby and Happy help Ralph, who is in the throes of his first crush.